We present MWE-Finder, an application that enables a user to search for multiword expressions (MWEs) in large Dutch text corpora. Components of many MWEs in Dutch can occur in multiple forms, need not be adjacent, and can occur in multiple orders (such MWEs are called flexible). Searching for such flexible MWEs is difficult and cannot be done reliably with most search applications. What is needed is a search engine that takes into account the grammatical configuration of the MWE. MWE-Finder is therefore embedded in GrETEL, a treebank search application for Dutch. A user can enter an example of a MWE in a specific canonical form, after which the system searches for sentences in which the MWE occurs, using queries generated automatically from the canonical form. We will describe in detail how the queries for this MWE are derived from the canonical form. The MWE can also be selected from a list of approximately 10k canonical forms for Dutch MWEs that MWE-Finder offers. We will show that MWE-Finder also offers facilities to find examples with unexpected modifiers or determiners on components of the MWE, and that it will yield statistics on the arguments, modifiers and determiners that occur with the MWE and its components.